1. Field of the Disclosure
The present disclosure relates to a motor, and more particularly, to a motor capable of reducing a cogging torque and being rotated with a high speed.
2. Description of the Related Art
A motor is a device for converting electric energy into mechanical energy, and is used in all kinds of devices as a driving source.
Motors are generally identified as either a direct current motor or an alternating current motor, according to a power source. The alternating current motor is classified into an induction motor, a synchronous motor, and a commutator motor.
A rotor of the synchronous motor includes a shaft, a plurality of core blocks coupled to the shaft, and a permanent magnet inserted into each of the core blocks.
When power is supplied to a stator of the motor, a magnetic force is generated between the permanent magnet of the rotor and a coil of the stator thereby causing rotation of the rotor. Herein, as a position of the permanent magnet is changed with respect to the stator, the magnetic force is changed. Accordingly, a cogging torque is generated. The cogging torque may cause noise and vibration of the motor.
In order to reduce the cogging torque, an insulating plate is disposed between the core blocks of the rotor. Then, the plurality of core blocks are laminated to each other so that the permanent magnets can be disposed in a zigzag form. Then, the core blocks are assembled to each other using one or more rivets. The above process is called a skew process. The permanent magnets of the core blocks are disposed so that each center thereof can have a phase difference from each other. Accordingly, when the rotor is rotated, an intensity of the magnetic force generated between the permanent magnet and the stator is gradually changed as a position of the permanent magnet is changed. As a result, the cogging torque is reduced.
When power is supplied to the stator, a magnetic force by the permanent magnet may be leaked to an outer circumferential surface of the core block without being attenuated at the coil of the stator. In order to solve the problem, a flux barrier is formed at both ends of the permanent magnet. Preferably, the flux barrier has a large size so as to minimize a flux leakage.
However, the conventional motor has high production costs at least due to the skew process by which a plurality of the core blocks are laminated to each other so that the permanent magnets can be disposed in a zigzag form, and due to the assembly of the core blocks to each other using one or more rivets.
Furthermore, the flux barrier is formed to have a large size, whereas a bridge formed between an outer circumferential surface of the core block and the flux barrier is formed to have a thin thickness. Accordingly, a structural intensity of the core block is low, and thus the bridge is deformed or damaged due to a strong centrifugal force when the rotor is rotated with a high speed.